Transition between different types of breakdown of the quantum Hall effectby illumination, temperature change and the application of gate voltage

We investigate the breakdown of the quantum Hall effect (QHE) and observe a remarkable change in dependence of the critical current for the breakdown in sample width. Both linear and sub-linear dependences of the critical cur rent on sample width are obtained for the same sample, depending on tempera ture, way of illumination, and gate bias voltage. The experimental results of the breakdown of the QHE are explained by comparing electron density flu ctuations, which are characterized by the random potential from the ionized donors and by screening effects, with the thermal broadening of the electr on energy distribution. It is suggested that the electron density fluctuati ons play an important role in the breakdown of the QHE. (C) 2001 Elsevier S cience Ltd. All rights reserved.